1. Field of the Invention
The present invention relates to a semiconductor device, a method of producing a semiconductor device, and a semiconductor substrate cleaning apparatus used for the production method. More particularly, the present invention relates to a semiconductor device production method including a step of cleaning an edge part of a semiconductor substrate and a semiconductor substrate cleaning apparatus used for the production method.
2. Description of the Background Art
Typically, in a method of producing a semiconductor device, a plurality of films are formed on a semiconductor substrate. There are cases in which, after a film such as aluminum is formed on a semiconductor substrate, the semiconductor substrate is moved to another film forming apparatus with an edge part of the semiconductor substrate held by a predetermined apparatus in order to form another film on the semiconductor substrate. If the film of aluminum adheres to the edge part of the semiconductor substrate, the film of aluminum adheres to the apparatus that holds the semiconductor substrate. Since this apparatus holds other semiconductor substrates, the apparatus may in some cases hold a semiconductor substrate on which a film of aluminum is not formed. In such a case, aluminum adheres as an impurity onto the semiconductor substrate on which a film of aluminum is not formed, thereby contaminating the semiconductor substrate. Because of this, impurity contamination spreads over the production line for producing semiconductor devices.
In order to prevent this, it is necessary to effectively remove films, products, foreign substances, and others that adhere to the edge part of the semiconductor substrate. Conventionally, in a process for producing a semiconductor device, in order to prevent the aforesaid contamination, a step of cleaning the edge part of the semiconductor substrate is carried out after a film is formed on the semiconductor substrate.
FIG. 6 is a cross-sectional view illustrating a conventional semiconductor substrate cleaning apparatus. In FIG. 6, the cleaning apparatus includes a buffer plate 101, a guide pin 102 mounted on buffer plate 101, a supporting shaft 12 that supports buffer plate 101, and a motor 13 connected to a rotation shaft.
A plurality of guide pins 102 are provided on buffer plate 101, and a semiconductor substrate 1 is held by guide pins 102. An electrically conductive film, a dielectric film, and others are formed on a surface of semiconductor substrate 1 that opposes buffer plate 101. A predetermined gap is provided between semiconductor substrate 1 and buffer plate 101 so that buffer plate 101 may not be brought into contact with the electrically conductive film, dielectric film, and others. Buffer plate 101 is connected to supporting shaft 12. Since supporting shaft 12 is connected to motor 13, supporting shaft 12 and buffer plate 101 can be rotated by motor 13. A sealing gas is supplied from supporting shaft 12 in the direction shown by an arrow 110. The sealing gas flows through a gap between buffer plate 101 and semiconductor substrate 1 in directions shown by arrows 111 and 112.
Next, a method of cleaning an edge part 1e in such a cleaning apparatus will be described.
A chemical liquid is jetted from a chemical liquid ejecting nozzle 105 onto a rear surface of semiconductor substrate 1, that is, a surface opposite to the surface where the electrically conductive film, oxide film, nitride film, and others are to be formed, in a direction shown by an arrow 106. During this period, semiconductor substrate 1 rotates in a predetermined direction. The chemical liquid is accumulated on semiconductor substrate 1 as shown by a dotted line 107, and this chemical liquid flows towards edge part 1e of semiconductor substrate 1. The sealing gas flows, in directions shown by arrows 111 and 112, along the surface on the side opposite to the surface where the chemical liquid is jetted. Because of this, the portion up to an equilibrium point 1b where the flow of chemical liquid meets the flow of sealing gas will be immersed in the chemical liquid. The distance from edge part 1e of semiconductor substrate 1 to equilibrium point 1b is substantially determined by the balance between the rounding of chemical liquid and the flow rate of sealing gas, the rotation number of semiconductor substrate 1, and the shape of buffer plate 101.
By a cleaning method such as described above, the cleaning process can be performed on the adhering films, products, and foreign substances that can be easily dissolved and removed by chemical reaction with the chemical liquid. However, if, for example, an underlayer liable to be dissolved in chemical liquid is present on the semiconductor substrate and the adhering film to be removed is present on the underlayer, one cannot use a chemical liquid having a high dissolving power, because the underlayer film is liable to be dissolved in the chemical liquid. For this reason, edge part 1e must be cleaned with a chemical liquid having a low dissolving power. In such a case, it is difficult to remove the adhering films, products, and foreign substances that adhere to edge part 1e. 
Moreover, the distance from edge part 1e to the equilibrium point 1b is greatly affected by the wetting power of the chemical liquid at edge part 1e (bevel part) of semiconductor substrate 1 and the permeating power of the chemical liquid as well. The cleaning process conditions such as the rotation speed of semiconductor substrate 1, the flow rate of supplying the chemical liquid, and the flow rate of supplying the sealing gas are individually set in accordance with the adhering films, products, and foreign substances to be dissolved with the chemical liquid. However, if the permeating power of the chemical liquid on the film is strong, it often happens that the area where semiconductor chips are to be produced cannot be maintained, because the chemical liquid permeates into the film.
Japanese Patent Laying-Open No. 10-189515 discloses a method of removing foreign substances on the peripheries of a substrate without affecting the central area of the substrate. By this method, one allows a plasma to be generated on the peripheries of the substrate and a gas activated by the plasma is sprayed onto the peripheral region from the rear surface side of the substrate to remove the unnecessary substances on the substrate peripheries. However, by this method, the cleaning power on the peripheries may not be satisfactory.
Further, Japanese Patent Laying-Open No. 5-211140 discloses a method of removing materials from the peripheries of a substrate. By this method, the peripheral part of the substrate is exposed to an etching atmosphere to smoothen the peripheral part. However, even by this method, there is a problem in that the substrate peripheries cannot be satisfactorily cleaned.
Furthermore, Japanese Patent Laying-Open No. 6-210454 discloses a method of performing a beveling process on a cut-retardant material. By this method, at the time of performing a beveling process on a perimetric edge part of a disk-shaped wafer while rotating the wafer, an aqueous electrolyte solution is supplied to the perimetric part of the wafer and a high-temperature plasma jet is jetted onto the perimetric part to which the aqueous electrolyte solution is supplied. However, by this method, there is a problem in that the electrolytic solution permeates into the inside of the wafer.